Sensor device and method for making

ABSTRACT

There is described an improved sensor device for detecting the presence or absence of fluid. The improved device comprises a housing member defining a chamber, a thermally conductive member within the chamber, a tip member secured to the housing and forming a closure for the chamber, a substantially solid substrate member within the chamber and adapted for being readily removed from the chamber, said substrate member having first and second spaced apart portions and an intermediate portion therebetween, electrical resistive heater means positioned on the intermediate portion of the substrate member, and first and second heat responsive members each having a free end adapted for engaging only when the temperature difference between the first and second spaced apart portions of the substrate member exceeds a predetermined level. An improved method for making the above described sensor device is also described.

United States Patent [1 1 Szevernyi et a1.

[ SENSOR DEVICE AND METHOD FOR MAKING [75] Inventors: Nikolaus A. Szevernyi; Walter W.

Bickmire, both of Warren, Pa.

[73] Assignee: GTE Sylvania Incorporated,

Stamford, Conn.

[22] Filed: May 3, 1974 [21] Appl. No.: 466,635

[4 1 Sept. 9, 1975 Primary ExaminerG. Harris Attorney, Agent, or Firm-Norman J. OMalley; Lawrence R. Fraley; Donald R. Castle 57 ABSTRACT There is described an improved sensor device for detecting the presence or absence of fluid. The improved device comprises a housing member defining a chamber, a thermally conductive member within the chamber, a tip member secured to the housing and forming a closure for the chamber, a substantially solid substrate member within the chamber and adapted for being readily removed from the chamber, said substrate member having first and second spaced apart portions and an intermediate portion therebetween, electrical resistive heater means positioned on the intermediate portion of the substrate member, and first and second heat responsive members each having a free end adapted for engaging only when the temperature difference between the first and second spaced apart portions of the substrate member exceeds a predetermined level. An improved method for making the above described sensor device is also described.

12 Claims, 3 Drawing Figures PATENTEB SEP 9:915

SHEET 1 [IF 2 SENSOR DEVICE AND METHOD FOR MAKING CROSS REFERENCE TO CO-PENDING APPLICATIONS A previous patent application, U.S. Ser. No. 349,290, filed Apr. 9, 1973 and now US. Pat. No. 3,810,143 discloses and claims a sensing apparatus and device and is assigned to the same assignee as the present invention. The present application comprises an improvement to this device as well as an improved method for making a sensor device.

BACKGROUND OF THE INVENTION This invention relates to fluid sensor devices and more particularly to devices capable of providing an indication when said fluid approaches a predetermined level.

Fluid sensor devices are well known in the art. The sensor device disclosed in the above described U.S. application readily provides a means for detecting the presence or absence of fluid at a predetermined level within a container. The device further includes both a means for compensating for varying temperature changes of the fluid being detected as well as a continuously actuated means for indicating when the detected condition existed.

With regard to sensor devices of the variety described above, it has become particularly desirable to provide a means whereby said devices may be more readily repaired in the event of failure. It has also been a desired requirement to provide a means whereby as sembly of said devices may be more readily facilitated.

It is believed therefore that a device for detecting the presence or absence of fluid at a predetermined level withina container which is more readily adaptable for both assembly and repair constitutes an advancement in the art. It is further believed that an improved method for making the described sensor device constitutes advancement in the art.

OBJECTS AND SUMMARY OF THE INVENTION It is therefore a primary object of this invention to provide an improved sensor device which is more readily adaptable for repair and assembly.

It is a further object of this invention to provide an improved method for making the described sensor de vice.

In accordance with one aspect of this invention there is provided an improved sensor device comprising a housing member defining a chamber, a thermally conductive member within said chamber, a tip member secured to said housing and forming a closure for said chamber, a substantially solid substrate member within said chamber adapted for being readily removed from said chamber, said substrate member having first and second spaced apart portions and an intermediate portion therebetween, electrical resistive heater means positioned on the intermediate portion of the substrate member, and first and second heat responsive members each having a free end positioned in heat conductive relationship to the electrical resistive heater means and adapted for engaging only when the temperature difference between said first and second spaced apart por tions of said substrate members exceeds a predetermined level.

In accordance with another aspect of this invention, there is provided an improved method for making a sensor device having a housing member defining a chamber, a thermally conductive member within said chamber, a tip member secured to the housing and forming a closure for the chamber, a substantially solid substrate member within the chamber having first and second spaced apart portions and an intermediate portion therebetween, electrical resistive heater means, and first and second heat responsive members each having a free end adapted for engaging only when the temperature difference between the first and second spaced apart portions of said substrate member exceeds a predetermined level. The improved method comprises positioning the electrical resistive heater means on said intermediate portion, securing the first and second heat responsive members to the first and second spaced apart portions respectively, and positioning said substrate member having said heater means and said first and second heat responsive members positioned thereon within the chamber of said sensor device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of one embodiment of the present invention.

FIG. 2 is an enlarged view of the sensor device of FIG. 1.

FIG. 3 is an exploded isometric view of two of the components of the sensor device of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above described drawings.

With particular reference to FIG. 1, one embodiment of a fluid detecting sensor device 10 in accordance with the invention is illustrated and shown to be positioned within a containter 11 adapted for holding a quantity of fluid 13 therein. Electrically joined to sensor device 10 is a current indicating means, illustrated as bulb 15, a switch 17, and a source of electrical potential 19. The described electrical circuit which operates in conjunction with sensor device 10 is illustrated as being grounded on the side of the potential source 19 opposing that of switch 17. Additionally container 11 is also established at ground potential. It is to be understood however that should container 11 be of an electrically nonconductive material, i.e. plastic, sensor device 10 would be at ground potential.

Although the particular embodiment illustrates sensor device 10 positioned within the side of container 11, the device may be placed in either the bottom or top of the container depending on the level of fluid to be detected or the configuration of the container. Furthermore, although the method shown for retaining sensor 10 in container 11 is by utilizing screw threads (the sensor being provided with external screw threads to mate with corresponding internal threads in container 11), other methods of retention are possible such as welding or soldering.

In FIG. 2, there is provided an enlarged sectional view of sensor device 10 as illustrated in FIG. 1. Sensor device 10 comprises a housing member 21 which defines a chamber 23, a thermally conductive member 25 positioned substantially within chamber 23, a tip member 27 secured to housing 21 and forming a closure for chamber 23, and a substantially solid substrate member 29 within chamber 23 and adapted for being readily removed from said chamber. Sensor device further comprises an electrical resistive heater means 31 positioned on substrate 29 and first and second heat responsive members 33 and 35 each having a free end adapted for engaging. Partially positioned within thermally conductive member 25 is a pair (only 1 shown in FIG. 2) of terminal members 37 and 37.

With particular reference to FIG. 3, there is shown an exploded isometric view of thermally conductive member 25 and substrate member 29 as they appear removed from the sensor devices housing member 21 and tip member 27; The described terminal members 37 and 37 are more clearly shown. A slot 39 is provided within an end of thermally conductive member 25 to provide a means whereby an end of substrate 29 may be slidably positioned within member 25 in order that contacting edges 41 and 41 of terminals 37 and 37' respectively make contact with desired portions on this end.

Substrate member 29 comprises a pair of first and second spaced apart portions 43 and 45. Substrate 29 further comprises an intermediate portion 47 positioned substantially between the described spaced apart portions. In the preferred embodiment, substrate 29 is comprised of a ceramic material. It is to be understood however that several electrically insulative materials are suitable for substrate 29, such as glass.

First spaced apart portion 43 has positioned thereon a pair of electrically conductive members 49 and 51 which are spaced apart in a nonconnecting manner. Similarly, second spaced apart portion 45 has positioned thereon an electrically conductive member 53. The preferred material for conductive members 49, 51, and 53 is a conductive paste of a silver-palladium composition which is preferably deposited on substrate 29 utilizing known silk screening techniques. Once deposited in a uniform manner, the described conductive members are subjected to relatively high temperatures to thereby render them substantially rigid.

Positioned on intermediate portion 47 of substrate 29 is an electrically resistive heater means 55. Heater means 55 is preferably of a Ruthenium blend and is deposited utilizing similar techniques to those for conductive members 49,50, and 51. Any other resistor paste utilizing metal powders and glass particles dispersed in an organic vehicle can also be successfully used. As illustrated, electrical resistive heater means 55 is in contact with and therefore electrically connected to electrical conductive members 51 and 53.

As illustrated in FIG. 3, first and second heat responsive members 33 and 35 are preferably positioned in a substantially perpendicular relationship to electrical resistive heater means 55, each having a free end positioned in a spaced relationship substantially directly above this heater means. Accordingly, the'opposing ends of each heat responsive member are affixed to a pair of upstanding bracket members 57 and 59. Bracket members 57 and 59 each have a base portion (57 and 59) which is adapted for being secured to the described first and second spaced apart portions 43 and 45 respectively. More specifically, base portion 57 of bracket 57 is secured to electrical conductive member 49 while base portion 59' of bracket 59 is secured to electrical conductive member 53. Both of the described bracket members are preferably of an electrically conductive material such as steel to provide a means whereby the described heat responsive members 33 and 35 may be electrically connected to members 49 and 53 respectively. During the operation of sensor device 10, the described free ends of the heat responsive members 33 and 35 are adapted for engaging when the temperature difference between the first and second spaced apart portions 43 and 45 exceeds the predetermined level. Thus a means is provided whereby electrical current may pass from electrical conductive member 49 to electrical conductive member 53. The source of this current is provided from the electrical circuit described in FIG. 1 as it passes from this circuit through therminal member 37 which in turn is electrically connected to electrical conductive member 49 when substrate 29 is positioned within slot 39 of the thermally conductive member 25. Electrical conductive member 53 on the other hand is electrically connected to a heat conductive spacing member 61 through interconnecting strip 60 to thus provide a means whereby the electrical current may pass to en gage tip member 27 and thus return to ground potential through container 11 (illustrated in FIG. 1 This is further achieved as a result of spacer member 61 being slidably engaged with the described tip member, as illustrated in FIG. 2. Spacer member 61 is preferably of copper or a similar sound heat conductive material which is also capable of conducting electrical current. In addition to providing a means for achieving the described electrical current path as well as a means for suitably spacing substrate member 29 from the internal walls of chamber 23 within sensor device 10, spacer member 61 also facilitates removal of the heat built up within chamber 23. This is achieved by providing a more direct means of thermal transmission of the described heat to tip member 27. As further illustrated in FIG. 3, a second heat conductive spacer member 63 is also provided and is positioned relative to the first spaced apart portion 43. Similarly to spacer member 61, this member provides a means whereby the removal of heat at this end of substrate 29 is more readily facilitated. That is, spacer member 63 provides a means whereby the heat built up in this portion of chamber 23 is more readily transmitted into the surrounding housing 21. Spacing member 63 is also preferably of copper or a similar good thermally conductive material.

It is understood however that spacer member 63 is not an essential component to the preferred embodiment of the invention and that substrate member 29, having the described heat responsive means suitably located thereon, may be placed within chamber 23 without including this component.

In operation, electrical current is supplied from potential source 19 through terminal member 37, electrical conductive member 51, electrical resistive heater means 55, electrical conductor 53, spacer member 61, tip member 27, housing member 21, into container 1 1, and back to ground potential. This continuously flowing current path will accordingly provide a means whereby the electrical resistive heater means 55 will become substantially heated thus providing heat to the heat responsive members 33 and 35. With fluid about tip 27 of the sensor device 10, the heat generated by heater means 55 is transmitted through tip member 27 into the surrounding fluid. Additionally, heat is also transmitted through spacer means 63 as well as the thermally conductive member 25 and therefore into housing 21 and the external environment surrounding the end of the sensor device external of container 11. The described opposing heat paths thus provide a means whereby the heat generated within chamber 23 may be equally transmitted in an opposing manner from sensor device 10. Should an imbalance in either of the described heat paths occur, such as by the removal of fluid 13 from about tip member 27, heat responsive members 33 and 35 will become engaged at their free ends. Accordingly, an alternate path for electrical current is now provided such that electrical current will flow through both of the engaged heat responsive members and through electrical conductive member 49 on first spaced apart portion 43. This current further flows through terminal 37 and into bulb within the electrical circuit. The bulb is now energized to provide an indication of the aforedescribed condition. Bulb 15 will be continuously energized due to the continuous passage of electrical current through the electrical resistive heater means 55., which will serve to continuously heat the engaged free ends of heat responsive members 33 and 35.

To assemble sensor device 10, the described bracket members 57 and 59 are secured in the illustrated manner to the respective conductive members 49 and 53 utilizing solder or similarly well known techniques. This is achieved after the described electrical conductive members 49, 51, and 53 and electrical resistive heater means 55 have been positioned on substrate 29. Substrate 29, with the described components in place, is then positioned within chamber 23 of housing 21. Thermally conductive member 25 is then positioned within housing 21 to provide the described sliding contact between terminals 37 and 37' and conductive members 49 and 51 respectively. It can be readily understood however that substrate 29, with the described components in place, can first be positioned within thermally conductive member 25 and thereafter this entire assembly inserted within housing 21.

Accordingly, a means has been described whereby sensor device 10 is more readily adaptive to repair in the event of failure. As explained, should device 10 fail or should it be desirable to replace components therein, it is only necessary to remove the thermally conductive member 25 and substrate member 29 from within housing 21, thereby leaving housing 21 within container 11. The described sensor device thus provides a means whereby the sensor may be repaired or components replaced therein without the necessity for removing the fluid within the described container.

Thus there has been provided a device for detecting the presence or absence of fluid at a predetermined level within a container. Unique features of this device include means whereby repair and assembly of the device are more readily achieved than in sensor devices known in the prior art. There has also been provided an improved method for making such a sensor device.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims. What is claimed is:

1. An improved sensor device comprising:

a housing member defining a chamber,

a thermally conductive member positioned substantially within said chamber,

a tip member secured to said housing and forming a closure for said chamber,

a substantially solid substrate member within said chamber and adapted for being readily removed from said chamber, said substrate member having first and second spaced apart portions and an intermediate portion therebetween, said first spaced apart portion in heat conductive relationship to said thermally conductive member, said second spaced apart portion in heat conductive relationship to said tip member;

electrical resistive heater means positioned on said intermediate portion of said substrate member, said electrical resistive heater means electrically insulated from said first spaced apart portion and electrically connected to said second spaced apart portion; and

first and second heat responsive members each having a free end positioned in heat conductive relationship to said electrical resistive heater means and adapted for engaging only when the temperature difference between the first and second spaced apart portions of said substrate member exceeds a predetermined level.

2. The sensor device according to claim 1 further in cluding means for securing said first and second heat responsive members to said first and second spaced apart portions respectively.

3. The sensor device according to claim 2 wherein said securing means comprises a pair of bracket members each having a base portion adapted for being affixed to one of said spaced apart portions and an upstanding wall portions adapted for having one of said heat responsive members affixed thereto.

4. The sensor device according to claim 1 wherein said first and second heat responsive members are positioned in a substantially perpendicular relationship to said electrical resistive heater means.

5. The sensor device according to claim 1 further including a heat conductive spacing member positioned relative to said first spaced apart portion of said substrate member.

6. The sensor device according to claim 1 further including a heat conductive spacing member positioned relative to said second spaced apart portion of said substrate member and in heat conductive relationship to said tip member.

7. The sensor device according to claim 1 wherein said thermally conductive member is adapted for being readily removed from said chamber.

8. The sensor device according to claim 7 wherein said thermally conductive member is further adapted for slidably engaging said substrate member within said chamber.

9. An improved method for making a sensor device having a housing member defining a chamber, a thermally conductive member positioned substantially within said chamber, a tip member secured to said housing and forming aclosure for said chamber, a substantially solid substrate member within said chamber, said substrate member having first and second spaced apart portions and an intermediate portion therebetween, electrical resistive heater means, and first and second heat responsive members each having a first end adapted for engaging only when the temperature difference between said first and second spaced apart portions of said substrate member exceeds a predetermined level, said method comprising:

positioning said electrical resistive heater means on said intermediate portion of said substrate member whereby said heater means is electrically insulated from said first spaced apart portion and is electrically connected to said second spaced apart portion; securingsaid first and second heat responsive members to said first and second spaced apart portions, respectively, whereby free ends of said heat responsive members will be positioned in heat conductive relationship to said heater means; and positioning said substrate member having said heater means positioned therein and said first and second heat responsive members secured thereto substantially within said chamber.

10. The method according to claim 9 further including the step of positioning a heat conductive spacing member relative to said first spaced apart portion of said substrate member prior to positioning said substrate member within said chamber.

11. The method according to claim 9 further including the step of positioning a heat conductive spacing member relative to said second spaced apart portion of said substrate member prior to positioning said substrate member within said chamber.

12. The method according to claim 9 including the step of positioning said first and second heat responsive members in a substantially perpendicular relationship to said electrical resistive heater means. 

1. An improved sensor device comprising: a housing member defining a chamber, a thermally conductive member positioned substantially within said chamber, a tip member secured to said housing and forming a closure for said chamber, a substantially solid substrate member within said chamber and adapted for being readily removed from said chamber, said substrate member having first and second spaced apart portions and an intermediate portion therebetween, said first spaced apart portion in heat conductive relationship to said thermally conductive member, said second spaced apart portion in heat conductive relationship to said tip member; electrical resistive heater means positioned on said intermediate portion of said substrate member, said electrical resistive heater means electrically insulated from said first spaced apart portion and electrically connected to said second spaced apart portion; and first and second heat responsive members each having a free end positioned in heat conductive relationship to said electrical resistive heater means and adapted for engaging only when the temperature difference between the first and second spaced apart portions of said substrate member exceeds a predetermined level.
 2. The sensor device according to claim 1 further including means for securing said first and second heat responsive members to said first and second spaced apart portions respectively.
 3. The sensor device according to claim 2 wherein said securing means comprises a pair of bracket members each having a base portion adapted for being affixed to one of said spaced apart portions and an upstanding wall portions adapted for having one of said heat responsive members affixed thereto.
 4. The sensor device aCcording to claim 1 wherein said first and second heat responsive members are positioned in a substantially perpendicular relationship to said electrical resistive heater means.
 5. The sensor device according to claim 1 further including a heat conductive spacing member positioned relative to said first spaced apart portion of said substrate member.
 6. The sensor device according to claim 1 further including a heat conductive spacing member positioned relative to said second spaced apart portion of said substrate member and in heat conductive relationship to said tip member.
 7. The sensor device according to claim 1 wherein said thermally conductive member is adapted for being readily removed from said chamber.
 8. The sensor device according to claim 7 wherein said thermally conductive member is further adapted for slidably engaging said substrate member within said chamber.
 9. An improved method for making a sensor device having a housing member defining a chamber, a thermally conductive member positioned substantially within said chamber, a tip member secured to said housing and forming a closure for said chamber, a substantially solid substrate member within said chamber, said substrate member having first and second spaced apart portions and an intermediate portion therebetween, electrical resistive heater means, and first and second heat responsive members each having a first end adapted for engaging only when the temperature difference between said first and second spaced apart portions of said substrate member exceeds a predetermined level, said method comprising: positioning said electrical resistive heater means on said intermediate portion of said substrate member whereby said heater means is electrically insulated from said first spaced apart portion and is electrically connected to said second spaced apart portion; securing said first and second heat responsive members to said first and second spaced apart portions, respectively, whereby free ends of said heat responsive members will be positioned in heat conductive relationship to said heater means; and positioning said substrate member having said heater means positioned therein and said first and second heat responsive members secured thereto substantially within said chamber.
 10. The method according to claim 9 further including the step of positioning a heat conductive spacing member relative to said first spaced apart portion of said substrate member prior to positioning said substrate member within said chamber.
 11. The method according to claim 9 further including the step of positioning a heat conductive spacing member relative to said second spaced apart portion of said substrate member prior to positioning said substrate member within said chamber.
 12. The method according to claim 9 including the step of positioning said first and second heat responsive members in a substantially perpendicular relationship to said electrical resistive heater means. 